The few healthcare workers remaining in Syria are working under insurmountable challenges.

The mass exodus of doctors from Syria has exposed remaining medical staff, some under-qualified and inexperienced, to perform operations under unimaginable conditions, according to a new report by a leading children's advocacy group.

A report by Save the Children said thousands of children were dying or at grave risk of chronic and preventable diseases that were rife due to the widespread destruction of Syria's healthcare system.

An estimated 15,000 doctors have fled Syria since the conflict began, representing half of the certified physicians in a country whose medical system was once touted as one of the best in the Arab world.

In some regions, the loss is particularly acute. According to a recent report by Physicians for Human Rights, by July 2013, only 250 physicians remained of the 6,000 who once practiced in Aleppo. The city was the largest in Syria with a population of 2.5 million before the civil war.

The World Health Organisation (WHO) estimates that number could be as low as 36 in Aleppo, which is "catastrophically far below" the organisation's minimum standard of 2,500 doctors for a population of that size.

According to the report, only 0.3% of the remaining healthcare staff at the country's 45 functioning public hospitals were qualified emergency doctors. Young doctors barely out of medical school were forced to perform hundreds of operations. In one case, the only practitioner to treat children was a dentist.

Healthcare workers were also sometimes forced to amputate the limbs of children with serious injuries because they lacked the equipment to treat them. Newborn babies were dying in incubators due to power cuts and some patients opted to be "knocked out with metal bars for lack of anaesthesia."

"The very notion that anyone would even consider this attests to how devastated the health system is," said Misty Buswell, regional advocacy director for Save the Children.

"Syrians themselves are making heroic efforts to assist children and others in need of healthcare, but those who remain are often not specialised in emergency medical care or surgeries."

She added that the health situation in Syria could even be worse than reports suggest due to the lack of accurate data and limited access to some areas in the country.

Speaking from Aleppo, Hassan Abdulaziz, the director of the Aleppo Medical Council, said he was working under dire conditions with a serious lack of equipment and staff. "We only have three orthopaedic surgeons serving more than one million people, two anaesthesiologists working intermittently, no radiologists and no cardiologists."

He said ambulances and medical equipment were often destroyed due to the increased number of aerial attacks on the city. "Medications, mainly anaesthesia drugs and consumables are hard to get in."

Another Syrian doctor who had fled from Damascus to the United States said it was common for nurses to perform surgical operations in areas where there were no doctors.

Speaking to Nature Middle East on condition of anonymity for fear of his family still in Syria, he told of an incident in which a paediatrician assisted a pregnant woman to deliver a baby with no training in obstetrics, since he was the only doctor in the area. "He used YouTube to familiarise himself with the procedure before he started."

The report called on all parties to the conflict to urgently implement the UN Security Council resolution to allow unfettered humanitarian access to all parts of Syria.